1. Field of the Invention
This invention relates to a self-centering, push-pull cable apparatus usable for automatically returning controllable mechanisms to a neutral, centered position.
2. Description of the Prior Art
Push-pull cables are used frequently to control the operation of remotely situated mechanisms such as hydraulic valves and similar devices which, in turn, may form part of the control system for machinery. In numerous applications, it is necessary that the controllable mechanism be movable to either side of a neutral, centered position. For example, with a hydraulic valve, this may be required to provide forward and reverse actuation of the machinery with which the valve is associated. In such situations, it is also sometimes desirable that the controllable mechanism normally return to its neutral, centered position when the actuating force applied to it is released. Where a push-pull cable apparatus is used to control the mechanism, this means that the cable should return to the neutral position after relaxing of the pushing or pulling input load applied to the cable.
In the past, spring devices have been available for use in connection with push-pull cables to provide the return action to the neutral position. In some installations, devices of this nature are typically connected to the control mechanism independently of the push-pull cable apparatus. Some of these constructions are capable of producing automatic return from a single direction while others provide for automatic return from actuated positions on either side of a neutral position.
With the prior art constructions described above, employment of a spring return device in association with a conventional push-pull cable becomes rather cumbersome. Special attachments must be provided for installation of the combined system. In addition, the separate and remotely situated spring return device requires additional space which may be a handicap where space is at a premium.